Many industrial processes use rolls to either treat or form a web of material. Typical of such applications is the papermaking process, in which, at various stages of the process the web of paper is passed between a nip or entrained about one or more rolls. During such a process, the rolls may pick up material from the web and thus contaminate the surface of the roll. Such contamination can lead to reduction in the quality of the process and may result in unsatisfactory material being produced.
It has previously been suggested to remove material from the roll by the application of a doctor blade against the roll surface. A doctor blade is a thin blade that scrapes the surface and removes the material. However, in practice it is found that the blade may not be effective to remove all the surface contamination and eventually the contamination will build up to impair the performance of the process. For example, in a papermaking process, it may be that rolls in a calendar stack are heated. Heating is sometimes used when papers of particular chemical compositions, such as, for example, relatively high clay or starch content and gloss finish are being produced. The warmth of the roll may tend to increase the tendency for clays, starch or other materials to build up on the rolls. In any case, it may be desirable to prevent or discourage the agglomeration of clays or other matter on the rolls.